1. Field of the Invention
This invention relates to the field of foot and ankle braces, and in particular to a foot and ankle brace which provides high strength, torsion resistance, a top sole support formed integrally as part of a one-piece shoe base main body, improved shock absorbing characteristics, a locking mechanism between the vertical uprights for the brace and the sides of the shoe base, and lightweight construction.
2. Description of the Prior Art
A number of orthotic braces, often referred to as "walkers" have been developed for aid in the rehabilitation of ankle fractures. The object of such braces is to immobilize the ankle and yet permit weight bearing and walking of the patient. Such braces are often used after an initial period of time in which the ankle is immobilized in a rigid cast. This invention relates to those ankle braces which permit the patient to walk with the brace in place.
While prior art walkers have provided many advantages to the patient when compared with a rigid cast, they also have disadvantages which have caused discomfort and anxiety in a patient. For example, the hard material from which the base or shoe portion of the brace is made imparts a substantial shock to the patient's foot and ankle for each step he or she takes. Furthermore, such prior art ankle braces, while providing a fixed vertical upright brace which can be bound to the leg of the patient below the knee, there is a tendency to deform the ankle brace by the constant application of rotational torque between the vertical upright and the shoe base portion. When the torque applied between the vertical uprights and the shoe base is sufficient to upset the initially prescribed angle between the two elements, the uprights become loose or are twisted, so that the ankle is maintained at an improper relationship relative to the leg. Walking in such distorted position can be painful, and cause obvious extreme difficulties if not discovered early and replaced with a new brace. Finally, prior art shoe bases have been constructed of several complex pieces making construction and stocking of different shoe sizes very expensive.
Some attempts have been made to overcome the deficiencies noted above. However, such attempts have been inadequate. For example, in U.S. Pat. No. 4,771,768, a rocker for the ankle brace is made from a high impact rigid plastic material with the top of the interior surface thereof being formed by the top edges of spaced apart and parallel longitudinal ribs integral with perpendicular spaced apart parallel lateral ribs molded into the inside bottom portion of the rocker. While such construction serves to reduce the weight of the shoe portion, it is complicated by the fact that two major structural portions of the shoe base must be molded in order to produce a composite shoe base. According to U.S. Pat. No. 4,771,768, the base portion is provided with upstanding ribs which support the undersurface of a foot pad. If molded, the interior surface upon which the foot pad rests is formed by the top edges of spaced apart and longitudinal ribs integral with spaced apart parallel lateral ribs. In other words, the foot pad is necessarily rather thick because it sits upon a matrix of rib edges and would otherwise cause discomfort to the wearer, because the tops of the ribs would impress upon the bottom of the wearer's foot. In the upper portion of this prior art device, means are provided for attaching straps, and for receiving the lower end of the vertical uprights. The bottom portion of the shoe base includes the bottom sole and the complex arrangement of upstanding ribs on the upper surface of the bottom sole plate. As a result, the shoe base of this prior art ankle brace necessarily requires the manufacturing and later assembling of two separate complex parts. Also, since the inner sole upon which the foot rests is not formed as part of the ribbed support construction, an exceptionally thick foot pad is required. Finally, in the molded version of the shoe base, any twisting torque applied to the shoe base from the uprights must be absorbed primarily by the bottom surface of the open top cellular shell. This means that, due to the length of the uprights, severe stress is applied to and resisted by the bottom surface of the shell. As a result, the bottom surface could buckle, or the connection between the upright and the shoe could develop fractures leading ultimately to breakage.
The shoe of U.S. Pat. No. 4,974,583 suffers from the same deficiencies as those discussed in connection with U.S. Pat. No. 4,771,768, inasmuch as the former also teaches the construction of the shoe to include a support surface formed by ribs whose edges support layers of plastic or plastic foam for receiving the sole of a patient's foot. Any open cellular shoe base having upstanding ribs upon which a soft foot pad is placed is subject to the same critique: 1) they offer a very uncomfortable foot support surface (being the tops of a ribbed matrix), and 2) they absorb twisting torque from the uprights basically at the floor level producing great stress at the upright/shoe base connection.
While most ankle braces appear to have a single pivotal joint joining the vertical braces with the shoe portion (e.g. U.S. Pat. No. 4,510,927), there have been some attempts to make the connection between the vertical uprights and the shoe base more resistant to torque applied forces. For example in U.S. Pat. Nos. 4,414,965 and 4,378,793, the vertical uprights are attached to the sole of the shoe portion by a number of screws passing through the bottom of the vertical uprights and into the side of the bottom sole of the shoe. Such arrangement holds the uprights snugly against the sides of the sole portion of the shoe, but falls short of resisting deformation upon the application of a large torque acting to rotate the vertical uprights relative to the plane of the shoe sole. Even a large number of screws would not prevent this from happening, since the sole is typically formed of a molded plastic material, and the screws would "give" in the sheer direction with even moderately applied torsional forces. Furthermore, when the vertical uprights are relatively thin, as they are in the latter-two-mentioned patents, the sides of the holes through which the screws pass will permit an unacceptable amount of rotation between the uprights and the shoe base due to tolerance of the hole sizes relative to the body of the screws and wear on the screws and on the interior surfaces of the holes in the bottom of the uprights.
It can generally be concluded that in all existing walkers, large torque forces or shear forces are transmitted through the bottom of the shoe which causes some deformation of the sole support at the patient's foot level.
Another problem with prior art ankle braces is the twisting off or slipping of the heel part of the sole relative to the main body of the shoe due to constant impact with the ground and the natural outurning of the shoe as the patient walks. In the past, this problem has been addressed by simply providing softer plastic material in the heel portion, but that solution is not entirely effective and gives a very unnatural feel to the shoe when walking.
Accordingly, there is a need in the art to provide an ankle brace assembly which is not subject to the deficiencies noted above. The present invention satisfies this need.